1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Software WEP encryption implementation 4 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi> 5 * Copyright 2003, Instant802 Networks, Inc. 6 */ 7 8 #include <linux/netdevice.h> 9 #include <linux/types.h> 10 #include <linux/random.h> 11 #include <linux/compiler.h> 12 #include <linux/crc32.h> 13 #include <linux/crypto.h> 14 #include <linux/err.h> 15 #include <linux/mm.h> 16 #include <linux/scatterlist.h> 17 #include <linux/slab.h> 18 #include <asm/unaligned.h> 19 20 #include <net/mac80211.h> 21 #include "ieee80211_i.h" 22 #include "wep.h" 23 24 25 int ieee80211_wep_init(struct ieee80211_local *local) 26 { 27 /* start WEP IV from a random value */ 28 get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN); 29 30 return 0; 31 } 32 33 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen) 34 { 35 /* 36 * Fluhrer, Mantin, and Shamir have reported weaknesses in the 37 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, 38 * 0xff, N) can be used to speedup attacks, so avoid using them. 39 */ 40 if ((iv & 0xff00) == 0xff00) { 41 u8 B = (iv >> 16) & 0xff; 42 if (B >= 3 && B < 3 + keylen) 43 return true; 44 } 45 return false; 46 } 47 48 49 static void ieee80211_wep_get_iv(struct ieee80211_local *local, 50 int keylen, int keyidx, u8 *iv) 51 { 52 local->wep_iv++; 53 if (ieee80211_wep_weak_iv(local->wep_iv, keylen)) 54 local->wep_iv += 0x0100; 55 56 if (!iv) 57 return; 58 59 *iv++ = (local->wep_iv >> 16) & 0xff; 60 *iv++ = (local->wep_iv >> 8) & 0xff; 61 *iv++ = local->wep_iv & 0xff; 62 *iv++ = keyidx << 6; 63 } 64 65 66 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, 67 struct sk_buff *skb, 68 int keylen, int keyidx) 69 { 70 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 71 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 72 unsigned int hdrlen; 73 u8 *newhdr; 74 75 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 76 77 if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN)) 78 return NULL; 79 80 hdrlen = ieee80211_hdrlen(hdr->frame_control); 81 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN); 82 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen); 83 84 /* the HW only needs room for the IV, but not the actual IV */ 85 if (info->control.hw_key && 86 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) 87 return newhdr + hdrlen; 88 89 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 90 return newhdr + hdrlen; 91 } 92 93 94 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 95 struct sk_buff *skb, 96 struct ieee80211_key *key) 97 { 98 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 99 unsigned int hdrlen; 100 101 hdrlen = ieee80211_hdrlen(hdr->frame_control); 102 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 103 skb_pull(skb, IEEE80211_WEP_IV_LEN); 104 } 105 106 107 /* Perform WEP encryption using given key. data buffer must have tailroom 108 * for 4-byte ICV. data_len must not include this ICV. Note: this function 109 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 110 int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key, 111 size_t klen, u8 *data, size_t data_len) 112 { 113 __le32 icv; 114 115 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 116 put_unaligned(icv, (__le32 *)(data + data_len)); 117 118 arc4_setkey(ctx, rc4key, klen); 119 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN); 120 memzero_explicit(ctx, sizeof(*ctx)); 121 122 return 0; 123 } 124 125 126 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 127 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 128 * buffer will be added. Both IV and ICV will be transmitted, so the 129 * payload length increases with 8 bytes. 130 * 131 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 132 */ 133 int ieee80211_wep_encrypt(struct ieee80211_local *local, 134 struct sk_buff *skb, 135 const u8 *key, int keylen, int keyidx) 136 { 137 u8 *iv; 138 size_t len; 139 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 140 141 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN)) 142 return -1; 143 144 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 145 if (!iv) 146 return -1; 147 148 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data); 149 150 /* Prepend 24-bit IV to RC4 key */ 151 memcpy(rc4key, iv, 3); 152 153 /* Copy rest of the WEP key (the secret part) */ 154 memcpy(rc4key + 3, key, keylen); 155 156 /* Add room for ICV */ 157 skb_put(skb, IEEE80211_WEP_ICV_LEN); 158 159 return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3, 160 iv + IEEE80211_WEP_IV_LEN, len); 161 } 162 163 164 /* Perform WEP decryption using given key. data buffer includes encrypted 165 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 166 * Return 0 on success and -1 on ICV mismatch. */ 167 int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key, 168 size_t klen, u8 *data, size_t data_len) 169 { 170 __le32 crc; 171 172 arc4_setkey(ctx, rc4key, klen); 173 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN); 174 memzero_explicit(ctx, sizeof(*ctx)); 175 176 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 177 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0) 178 /* ICV mismatch */ 179 return -1; 180 181 return 0; 182 } 183 184 185 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 186 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 187 * ICV (4 bytes). skb->len includes both IV and ICV. 188 * 189 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 190 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 191 * is moved to the beginning of the skb and skb length will be reduced. 192 */ 193 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 194 struct sk_buff *skb, 195 struct ieee80211_key *key) 196 { 197 u32 klen; 198 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 199 u8 keyidx; 200 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 201 unsigned int hdrlen; 202 size_t len; 203 int ret = 0; 204 205 if (!ieee80211_has_protected(hdr->frame_control)) 206 return -1; 207 208 hdrlen = ieee80211_hdrlen(hdr->frame_control); 209 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN) 210 return -1; 211 212 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN; 213 214 keyidx = skb->data[hdrlen + 3] >> 6; 215 216 if (!key || keyidx != key->conf.keyidx) 217 return -1; 218 219 klen = 3 + key->conf.keylen; 220 221 /* Prepend 24-bit IV to RC4 key */ 222 memcpy(rc4key, skb->data + hdrlen, 3); 223 224 /* Copy rest of the WEP key (the secret part) */ 225 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 226 227 if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen, 228 skb->data + hdrlen + 229 IEEE80211_WEP_IV_LEN, len)) 230 ret = -1; 231 232 /* Trim ICV */ 233 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN); 234 235 /* Remove IV */ 236 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 237 skb_pull(skb, IEEE80211_WEP_IV_LEN); 238 239 return ret; 240 } 241 242 ieee80211_rx_result 243 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 244 { 245 struct sk_buff *skb = rx->skb; 246 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); 247 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 248 __le16 fc = hdr->frame_control; 249 250 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc)) 251 return RX_CONTINUE; 252 253 if (!(status->flag & RX_FLAG_DECRYPTED)) { 254 if (skb_linearize(rx->skb)) 255 return RX_DROP_UNUSABLE; 256 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 257 return RX_DROP_UNUSABLE; 258 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 259 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + 260 IEEE80211_WEP_IV_LEN)) 261 return RX_DROP_UNUSABLE; 262 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 263 /* remove ICV */ 264 if (!(status->flag & RX_FLAG_ICV_STRIPPED) && 265 pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN)) 266 return RX_DROP_UNUSABLE; 267 } 268 269 return RX_CONTINUE; 270 } 271 272 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 273 { 274 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 275 struct ieee80211_key_conf *hw_key = info->control.hw_key; 276 277 if (!hw_key) { 278 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, 279 tx->key->conf.keylen, 280 tx->key->conf.keyidx)) 281 return -1; 282 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) || 283 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) { 284 if (!ieee80211_wep_add_iv(tx->local, skb, 285 tx->key->conf.keylen, 286 tx->key->conf.keyidx)) 287 return -1; 288 } 289 290 return 0; 291 } 292 293 ieee80211_tx_result 294 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) 295 { 296 struct sk_buff *skb; 297 298 ieee80211_tx_set_protected(tx); 299 300 skb_queue_walk(&tx->skbs, skb) { 301 if (wep_encrypt_skb(tx, skb) < 0) { 302 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 303 return TX_DROP; 304 } 305 } 306 307 return TX_CONTINUE; 308 } 309